package linkedList;

public class LinkedList<E> {
    private class Node{
        public E e;
        public Node next;

        public Node(E e,Node next){
            this.e = e;
            this.next = next;
        }

        public Node(E e){
            this(e,null);
        }

        public Node(){
            this(null,null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    private Node dummyHead;
    private int size;

    public LinkedList(){
        dummyHead = new Node(null,null);
        size = 0;
    }

    //获取链表中的元素个数
    public int getSize(){
        return size;
    }

    //链表是否为空
    public boolean isEmpty(){
        return size == 0;
    }

    //在链表头添加新的元素
    public void addFirst(E e){
        add(0,e);
    }

    //在链表的index（0-based）的位置添加新的元素
    //在链表中不是一个常用的操作，练习用：
    public void add(int index,E e){
        if(index < 0 || index > size){
            throw new IllegalArgumentException("Add failed,Illegal index");
        }
        Node prev = dummyHead;
        for(int i = 0;i < index ;i++){
            prev = prev.next;
        }
//            Node node = new Node(e);
//            node.next = prev.next;
//            prev.next = node;
        prev.next = new Node(e,prev.next);
        size ++ ;

    }

    //在链表末尾添加元素e
    public void addLast(E e){
        add(size,e);
    }

    //获取链表的第index的位置的值
    public E get(int index){
        if(index < 0 || index > size){
            throw new IllegalArgumentException("Add failed,Illegal index");
        }

        Node cur = dummyHead.next;
        for(int i = 0; i<index ;i++){
            cur = cur.next;
        }
        return cur.e;
    }

    //获得链表的第一个元素
    public E getFirst(){
        return get(0);
    }

    //获得链表的最后一个元素
    public  E getLast(){
        return get(size-1);
    }

    //修改链表的第index个位置元素为E
    public void set(int index,E e){
        if(index < 0 || index > size){
            throw new IllegalArgumentException("Add failed,Illegal index");
        }

        Node cur = dummyHead.next;
        for(int i = 0; i<index ;i++){
            cur = cur.next;
        }
        cur.e = e;
    }

    //查找链表中是否存在元素e
    public boolean contains(E e){
        Node cur = dummyHead.next;
        while (cur != null){
            if(cur.e.equals(e)){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    //从链表中删除index位置的元素，返回删除的元素
    public E remove(int index){
        if(index < 0 || index > size){
            throw new IllegalArgumentException("Add failed,Illegal index");
        }

        Node prev = dummyHead;
        for(int i = 0; i<index ;i++){
            prev = prev.next;
        }

        Node reNode = prev.next;
        prev.next  = reNode.next;
        reNode.next = null;
        size --;
        return reNode.e;
    }

    //从链表中删除第一个元素
    public E removeFirst(){
        return remove(0);
    }

    //从链表中删除最后一个元素
    public E removeLast(){
        return remove(size -1);
    }

    //从链表中删除元素
    public void removeElement(E e){
        Node prev = dummyHead;
        while(prev.next != null){
            if(prev.next.e.equals(e)){
                break;
            }
            prev = prev.next;
        }

        if(prev.next != null){
            Node delNode= prev.next;
            prev.next = delNode.next;
            delNode.next = null;
        }
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        Node cur = dummyHead.next;
        while (cur != null){
            res.append(cur.e + "->");
            cur = cur.next;
        }
        res.append("NULL");
        return res.toString();
    }

    public static void main(String[] args) {
        LinkedList<Integer> linkedList = new LinkedList<Integer>();
        for(int i = 0; i < 5; i++){
            linkedList.addFirst(i);
            System.out.println(linkedList);
        }
        linkedList.add(2,666);
        System.out.println(linkedList);
        linkedList.remove(2);
        System.out.println(linkedList);
    }
}
